1. Field of the Invention
The present invention relates to a panel-shaped frame used for a seat back of a vehicle seat and a seat back having the frame.
2. Description of the Related Art
In a field of a seat used for a vehicle such as an automobile, there have been used various seat back frames (hereinafter, simply referred to as a frame) for a seat back configured to support a back of a passenger. For example, a wide panel-shaped frame is used for a seat designed such that a seat back is laid down forwards to thus arrange a backside thereof to be substantially horizontal and a luggage is loaded on the backside. For example, JP-A-2011-105050 discloses a structure referred to as a so-called trunk through in which when a seat back of a seat of a rearmost raw is laid down forwards, the long luggage can be loaded from a trunk room to the seat back.
Generally, a steel plate has been used for such panel-shaped frame. However, since an area of the frame is large, a weight of the seat back increases. Therefore, like a frame 910 shown in FIG. 2, a plate thickness of a steel plate 930 is made as thin as possible so as to lighten the frame, and then, undulations referred to as beads 930a are provided, so that the stiffness necessary for a skeleton of the seat back is supplemented.
Also, even though the seat is designed such that a height of a headrest provided for a seat back cannot be adjusted, a stay 946 cannot be directly fixed to the thin steel plate 930 and needs be fixed through a bracket 945 which is separately prepared. In the meantime, the frame 910 is welded with a plurality of separate components such as a bracket 941 for attaching the seat back to a vehicle body, a bracket 943 for attaching an arm rest to the seat back, a striker 947 of a lock mechanism for fixing the seat back at an upright state, and the like.
A surface material such as a carpet is typically provided on the backside of the steel plate. Even when the surface material is provided on the backside, if the beads are provided below the surface material, the touch feeling would deteriorate when the passenger touches it or the outer appearance of the provided surface material would deteriorate.